MRF/AVN/GDAS CHANGES SINCE 1991

History of recent modifications to the global forecast/analysis system

• Pre-1991
  • 08/80: R30L12
  • 10/83: R40L12
  • 04/85: MRF85 R40L18 - GFDL physics
  • 06/86: MRF86 R40L18 - convection to tropopause
  • 08/87: MRF87 T80L18 - diurnal cycle, moisture all layers
  • 01/88: MRF88 T80L18 - interactive clouds
• 03/91: T80L18 to T126L18, silhouette to mean orog, new SST, marine stratus, reduced horizontal diffusion
• 06/91: SSI analysis
• 08/93: Arakawa-Schubert convection, 28 layers
• 01/95: SSM/I PW over sea; analysis changes; various physics changes (TPB 417 (not on Web))
• 10/95: Satellite radiances instead of T retrievals; ERS-1 winds; physics changes (TPB 428 (not on Web))
• 06/96: Adjustments to PBL and convection
• 02/97: SSM/I water vapor discontinued
• 11/97: Elimination of "valley snow" and other small changes (TPB 443)
• 01/98: TOVS-1b radiances; vertical diffusion inc in free atmosphere (TPB 445)
• 06/15/98: T170L42 to day 3.5; physics changes; 3D ozone; analysis changes (See TPB 449)
• 07/22/98: First emergency implementation: fix to convection, horizontal diffus, plant evap: see last section of TPB 449 above.
  
• 10/06/98: Second emergency implementation: Back to T126L28, better fits to data, more iterations in analysis, physics changes (TPB 450)
• 12/01/98: Snow resolution increased from 2.0 to 0.5 degrees; snow depth field added; snow depth no longer estimated by model
• 01/08/99: Use of VAD winds eliminated due to problems with light wind speeds
• 03/08/99: Introduction of high-resolution data from the NOAA-15 satellite. The data are radiances from the AMSU-A and HIRS-3 intruments. The NOAA-11 Satellite is no longer providing AMSU data and will soon be unable to provide HIRS data.
• 01/24/2000: Resolution upgraded from T126L28 to T170L42, restoring the resolution used from June 15 through Oct 5, 1998. No other changes in the forecast/analysis system. The MRF is run at T170L42 through day 7, then at T62L28 through day 16. The AVN is run at T170L42 out to 84 hours four times a day. (See TPB 452)
• 05/17/2000: AVN available out to 126h at full (T170) resolution at 00Z and 12Z.
• 06/27/2000: Resolution of ensemble members increased from T62 to T126 for first 60 hours of forecast.
• 07/06/2000: Hurricanes and tropical storms in the model's guess field are relocated to the official Tropical Prediction Center position in each 6-hour analysis cycle. ( TPB 472)
• 08/29/2000 18Z: Data cutoff time for the 06Z and 18Z final analysis (FNL) extended from 4 hours to 6 hours.
• 10/01/2000 06Z: Package of minor changes:
  Observations and analysis:      New obs error diagnosis,rawinsonde radiation correction, effects of balloon drift in time and space included
  Forecast and post processing:      Improved orography, reduced gaussian grid over polar regions, new surface albedo climatology, single scattering albedo adjusted
• 11/01/2000 12Z: ERA wind data erratic; turned off.
• 02/13/2001 12Z: Satellite radiance and moisture analysis changes plus smoothed output MSLP.
• 05/15/01 12Z: (See TPB 484).
  • Inclusion of cloud condensate as a history variable
  • Use of the cloud condensate in the calculation of radiative transfer
  • Stronger quality control for AMSU radiances
  • Momentum mixing included in deep convection
  • Refinement of hurricane relocation algorithm
  • SST anomaly damped toward climatology during forecast, with 90-day relaxation time
• 06/27/01 12Z: Minor increase in vegetation fraction.
• 07/24/01 12Z: The data source for the daily 1-degree sea surface temperature analysis is changed from NOAA-14 to NOAA-16 due to instrument drift.
• 08/15/2001 06Z: Package of minor changes:
  Observations and analysis:      Higher resolution sea ice mask
  Forecast and post processing:      Bug corrections in gravity wave drag, randomization of convective cloud tops, land surface evaporation with trace snow cover; minor adjustments in effective radius for ice crystals, autoconversion rate for ice, evaporation of falling precip, and critical RH for condensation
• 10/09/2001: Snow depth is updated daily at 00Z from observations; at 06Z, 12Z and 18Z the model guess is used. Formerly the same 00Z update was reinserted in each of the day's cycles.
• 01/15/2002 12Z: Quikscat surface winds included.
• 03/05/2002 : AVN runs four times a day out to 384 hours. Resolution is T170L42 to 180h, thereafter T62L28.
• 04/23/2002 00Z: MRF is replaced by the 00Z AVN. Look-alike MRF grids will still be available daily for several months on th ftp server at ftp://ftpprd.ncep.noaa.gov/pub/data/nccf/com/mrf/para/
• Sept-Oct 2002: Name changes: The AVN will be referred to as the Global Forecast System model (GFS).
• 10/29/02 12Z:(See draft TPB)
  • Resolution change
      old: T170L42 to 180h, T62L28 to 384h
      new: T254L64 to 84h, T170L42 to 180h, T126L28 to 384h
  • Analysis and observation changes: background error recomputed, AMSU-A channels 12 and 13 from NOAA-15 and NOAA-16 and HIRS from NOAA-16 used, METAR surface pressure observations used, divergence tendency constraint in tropics turned off.
• 03/11/03 12Z: NOAA 17 1B radiances assimilated, NOAA-16 AMSU-A radiances restored, QuikSCAT winds superobbed at 0.5 degrees.
• 08/28/03 12Z: RRTM longwave radiation from AER installed: More trace gases (CH₄, N₂O, CFC's) and better tropospheric water vapor absorption.
• 10/28/03 12Z: NOAA-17 AMSU-A radiances turned off
• 11/20/03 12Z: Package of minor analysis changes (see description)
• 12/09/03 12Z: Vertical diffusion added to ozone
• 02/24/04 12Z: Mountain blocking: Parameterization of the separation of airflow in the vertical with passage over mountainous terrain.
• 03/09/04 12Z: Ensemble run 4 times daily. Resolution T126 0-180 h, then T62 to 384 h.
• 05/25/04 12Z: Turn off NOAA-16 HIRS/3 observations
• 05/31/05 12Z:(See TPB - includes changes made 06/14/05 and 07/07/05)
  • Resolution change:
      old: T254L64 to 84h, T170L42 to 180h, T126L28 to 384h
      new: T382L64 to 180h, T190L64 to 384h
  • Increase mountain blocking, decrease vertical diffusion and modify sea ice.
  • Land Surface Model: Upgraded from OSU 2-L LSM to 4-L NOHA LSM.
• 06/14/05 12Z: Increase canopy resistance of vegetation
• 07/07/05 12Z: Correct error in temperature near top of model
• 01/31/05 18Z: Radiation code corrected to prevent blowups in ensemble forecasts
• 05/30/06 12Z: GFS Ensembles now have 14 members, 4 times daily. Each cycle now has its own control member. Resolution is T126L28 through 384 h. New ensemble transform method used to generate members.
• 08/22/06 12Z:(See Briefing Notes):
  • New orography&land-sea mask, improved snow analysis, and new ozone physics.
  • New glacial ice and fix error in downward LW radiation at earth's surface.
  • Infrastructure changes (e.g. Full ESMF compliance).
• 05/01/07 12Z:(See Briefing Notes):
  • Unify the NCEP 3DVAR assimilation system under the GSI, improving some performance metrics without affecting others and preparing for future analysis improvements.
  • Change vertical coordinate to hybrid sigma-pressure, reducing some upper air model errors.
  • Add new observing systems.
  • Modernize the radiation package.
  • Increase output particularly for hydrology.